In general, most conventional injection molding machines adopt a mold clamping apparatus for clamping and opening a mold. With reference to FIG. 6 for a general toggle injection molding machine as disclosed in R.O.C. Utility Model No. 522922, the toggle injection molding machine uses a toggle link rod set and a hydraulic cylinder extended outside the machine to push and move a movable mold base to perform the mold opening and clamping stroke. However, the distance of the hydraulic cylinder extended out of the aforementioned toggle injection molding machine is very large, so that it takes more space for packaging and transporting the machine and incurs higher packaging and transportation costs. In addition, the hydraulic cylinder also requires a larger space for the installation of the injection molding machine in a factory, and thus causing problems for the site planning of the factory and troubles for the installation of the injection molding machine.
With reference to FIGS. 1 to 5 for U.S. Pat. No. 6,520,766 issued to the discloser of this disclosure, the injection molding machine has a toggle link rod set pivoted between a bearing disc and a movable mold base, and the bearing disc and the movable mold base are disposed on a tie bar, and a link base is movably sheathed on the tie bar between the bearing disc and the movable mold base, and the link base is movably pivoted to a third arm of the toggle link rod set. In the meantime, a transmission member is installed on the link base, and the power source of the transmission member drives a threaded socket in the link base to rotate, and a ball screw is screwed into the threaded socket, and the front end of the ball screw is fixed to the backside of the movable mold base, so that when the power source drives the threaded socket to rotate, the threaded socket is moved on the ball screw to drive the link base to displace, so as to drive the toggle link rod set to push the movable mold base to perform the stroke of clamping and opening a mold and the transmission mechanism for driving the operation of the toggle link rod set and the movable mold base is installed in the machine. Therefore, the assembling space and the packaging and transportation costs can be saved.
In the actual manufacturing process, the discloser finds out that the mold clamping apparatus of the injection molding machine has the following drawbacks:
1. The threaded socket of the aforementioned patent requires a lubricating oil filled into the threaded socket in order to drive the ball screw to move, but the threaded socket has to rotate, so that an oil filling hole cannot be formed on the threaded socket, and an oil supply hole is formed at the center of the ball screw and communicated with the threaded socket for filling the lubricating oil. Obviously, such conventional molding machine is inconvenient.
2. The ball screw of the aforementioned patent must be a hollow rod, but the hollow rod not just reduces the structural strength of the ball screw only, but also shortens the service life and increases the manufacturing cost of the machine.
3. The first end of the ball screw of the aforementioned patent is connected to the center of the movable mold base, so that the mold ejector pins of the movable mold base must be installed on both sides of the stationary mold base, and thus increasing cost.
4. When the threaded socket is moved on the ball screw in accordance with the aforementioned patent, larger threaded socket and bearing are required, and the load of the motor for driving and rotating the threaded socket, and thus increasing the loss of electric power.